Production of artificial fibers from fiber forming liquids



jaw 29 1943. A, FORMHALS PRODUCTION OF ARTIFICIAL FIBERS FROM FIBER FORMING LIQUIDS Filed March 8, 1940 3mm Hm @021 Formhafis atented June 29, 1943 PRODUCTION oi ARTIFICIAL FIBERS FROM FIBER FORMING LIQUIDS Anton Formhals, Mainz, Germany; vested in the Alien Property Custodian Application March 8, 1940, Serial No. 323,036

In Germany May 13, 1939 4 (Claims. (01. l8-8 This invention relates to a process for the production of artificial fiber from fiber forming liquids under the application of an electrical high potential field to cause the formation of fibers, said field being maintained between an electrode preferably arranged at the source of liquid supply and a counter-electrod of opposite polarity spaced apart from said electrode. The production of artificial fibers from fiber-forming liquids under the application of an electrical high. potential field-briefly called electrical spinningis well known in itself. The effect of the electrical spinning method seems to be such that the colloidal particles of the fiber-forming liquidispinning solution) appear to be uniformly charged under the influence of the one field electrode, with the resulting effect that in the high-voltage field the. particles of the liquid repel each other and become disrupted so that the dissolved matter of the thus suddenly atomised spinning liquid is transformed into fibers while the solvent agent evaporates, the fibers being then attracted by the counter-electrode of the high potential field.

The hitherto known electrical spinning methods, however, could not be adopted by the industry, as all these methods were subject to deficiencies, particularly the fault that the fibers formed settled on the counter-electrode into a wedding-like mass which was quit unsuited for the further working-up into textile materials, es-

pecially since it was thus not possible to sufficiently dry the formed fibers within the range of the high potential field so that the deposited fibers therefore stuck fast to each other.

This substantial disadvantage has been eliminated in the process according to my copending application for U. S. patent filed August 16. 1938. Ser. No. 225,207, by the provision that at the counter-electrode such a high field intensity is produced as to revert the fiber-attracting effect of the counter-electrode-just before the latter is reached by the fibers-into a repelling effect so that a settling of the fibers on the counterelectrode is prevented.

The said patent specification illustrates also some examples of arrangements to be provided for the accomplishment of this method. in this process, the fibers formed which have been first attracted by the counter-electrode and then repelled again due to a reversal of their charge get into a state of suspension or equilibrium in a zone between-the two electrode which is neutral regarding attraction and repulsion. In this neu- "tral zone the fibers settle together into a fiber band, which may be then continually drawn out of the electrical field. withouthaving come in contact with the counter-electrode. By this method the said fiber band functions as an auxiliary electrode and a support for the settling or deposition of th subsequently formed fibers.

This method gives quite satisfactory results. However, in accordance with requirement for the continuous operation on a lar e industrial scale, with regard to the recovery of the evaporated solvent agent of the spinning solution on the one hand and to th 'maintenance of uniform atmospherical conditions within the spinning field on the Other hand, difficulties are encountered especially with the usual spinning chamber having insulated internal wall surfaces. During such continuous operation dimculties arise due to the fact that the formed fiber-band break or that during the formation of the fibers and their deposition the general cooperation between the individual rows of electrode nozzles which deliver the spinning solution and their associated counter-electrodes does not take place in the desired manner. These diificulties seem to be caused by the fact that the insulating walls of the spinning chamber become electrically charged which result in electrical disturbances and obstructions within the high potential field whereby the spinning operation is affected.

According to the present invention, it has been found that these troubles can be eliminated either by using a spinning chamber which consists of an electrically conductive material and is grounded or by using a spinning chamber which consists of an insulating material but has an inner walling of an electrically conductive material which i grounded. A substantial improvement of this invention, when compared with the process according to my co-pending application above identified provides for an arrangement by means of which the potential differences of the two electrodes may be altered relative to each other, so that the position of the above mentioned neutral zone between the two high potential electrodes may be displaced, i. e. for example with reference to the negative electrode may be raised or lowered. By this possibility of displacing the position of the neutra zone, the spinning process can be continually accommodated to the existing properties of the solutions to be spun as well as to the atmospheric conditions in the spinning chamber, so

that a breakage of the formed fiber-band is prevented a far as possible by an exact regulation of its position between the two electrodes.

Furthermore, it has been found that the strength of the fiber band can be increased by drawing same out of the electrical field through a fast rotating funnel, whereby the fiber band may be passed through the funnel either centrically or eccentrically. In this way, the loose fiber band receives a certain twisting so that a more compact and stronger fiber band will be obtained in the developing zone. Thereby, the eccentrical passage of the fiber-band through the rotating funnel has the advantage that any impurities such as unevaporated liquid-droplets which may have remained on 'the fibers are whirled ofi by centrifugal force, which contributes to a further drying of the fibers. The thus obtained fiber band may be used directly or provided with a twisting (1 to 2 turns per 1 cm.) for the warp and weft in the weaving mill and may be also drawn out without furtherance intofine yarns on cottonor wool-spinning machines.

In order that in exhausting and recovering the evaporated solvent agent of the spinning solution, the same atmospheric conditions permanently are maintained in the spinning chamber it is also desirable to have the air disturbed or rolled round according to methods which are generally known, for instance, the Biickler method.

The mentioned invented improvements of the electrical spinning method as per my copending application above identified are explained in detail in the following description whereby reference is made to the drawing which is a diagrammatic section of an example of the spinning chamber and the electrical equipment pertaining to same. I

In this drawing, i is the spinning chamber to the invention, the spinning chamber I is made of an electrically conductive material or covered inside with such a material and grounded through line 5. The spinning solution is delivered to the row of nozzles 2 under a. pressure through the pipe 6.

If a high potential field is produced between the two electrodes 3, 4, a transmutation of the liquid evolved from nozzles 3 into fibers takes place in this field, as specified in my copending application above identified, these fibers being attracted by the counterelectrode 4. If, however, on the.counterelectrode 4 a high field intensity is produced, then, as described in detail in my copending application above identified, the fiber attractin effect of the counterelectrode is converted into a repelling effect, just before the fibers have reached the counterelectrode, with a simultaneous reversal of the electrical charge of the fibers, so that the fibers cannot settle on the counterelectrode; that means, according to the. process in question, that the fibers in the proximity of the counterelectrode 4 get into a state oi equilibrium or suspension, i. e. into a neutral zone where the attraction and repulsion are equilibrated, and in this neutral zone the fibers consolidate into a fiber band I, and this band may then be drawn out of the electrical field.

In order to be able to displace the position of the mentioned neutral zone between the two high potential electrodes 3, t in accordance with the properties of the liquid to be spun, one may, for example, if an alternating current plant is used for the production of the high potential field, proceed among others in such a way that two rectifier plants are included in the line of the current transformed up to the high potential, and coupled. For instance, the first rectifier plant G1 may deliver a potential of 50 RV. against earth. The minus pole 8 of this rectifier plant is grounded through line 9 and connected through line l0 with the grounded walling of the spinning chamber I. The positive pole Il may, for instance, be connected through a resistance W1 by line I2 with the nozzle pipe 2. Thus, the potential of this rectifier plant can be regulated by the arrangement of transformer T1 practically from 0 to 50 kv. The second rectifier plant G2 is also laid out for a. direct voltage of 50 kv. The plus-pole I! of this plant is grounded through line M, whereas the minus-pole I5 is connected through a safety resistance W: by line IS with the counterelectrode 4 of the spinning chamber. The voltage of this second rectifier plant may be also regulated by a transformer T2 from 0 to 50 kv. maxim. in comoff from spinning chamber I through funnel I1 which has been put into fast rotation by electromotor i8 and then wound on reel l9. During the whole spinning operation, the air in the spinning chamber is being rolled round in accordance with Well known methods, and the solvent agent evaporated from the spinning solution is exhausted from the spinning chamber in such a way that the air in the chamber remains continually saturated with vapors of the solvent agent.

Having thus described the nature of the said invention and the best means I know of carrying the same into practical effect, I claim:

1. Apparatus for producing artificial fibers from fiber forming liquid which comprises a spinning chamber having electrically conductive but grounded internal walls, a first electrode and a counter-electrode of opposing polarity spaced apart within said spinning chamber, means for providing a high potential electric field between said electrodes and adapted to independently vary the potential difference at either electrode, nozzle means for supplying fiber forming liquid to said high potential field, and means for withdrawing the formed fibers from said field.

2. Apparatus as in claim 1, wherein the means for providing a high potential electric field between said electrodes and adapted to independently vary the potential difference at either electrode comprises in combination one high tension transformer in series with-a rectifier having its positive terminal connected with the first electrode and its negative terminal grounded, and another high tension transformer in series with a second rectifier having its negative terminal connected with said counterelectrode and its positive terminal grounded.

3. The combination as in claim 1, wherein the means for withdrawing the formed fiber from the high potential field comprises a rapidly rotating funnel through which the formed fibers are drawn.

4. The method of producing artificial fibers from. a fiber forming solution which comprises providing a high potential electric field in a spinning chamber, having its internal walls electrically conductive but grounded, thus rendering them immune to charge, between one electrode and a counterelectrode of opposing polarity spaced apart from said first electrode, passing a stream of fiber forming solution into said high potential field through said first electrode to thereby disrupt said solution into fibers and vapor, maintaining the field intensity at the counterelectrode of suflicient magnitude to exert a repelling effect on said formed fibers before they contact and deposit on said counterelectrode whereby said formed fibers attain a condition of floating equilibrium in a neutral zone substantially equilibrated as to attraction and repulsion, withdrawing said fibers in. the form of strands from said high potential electric field, subjecting said strands to a twisting action while within said spinning chamber and during the course of withdrawal, revolving the atmosphere in the 

